Muneaki Ishida

Disturbance observer-based motion control of direct drive motors

Simple and high-performance path tracking control and force control based on an acceleration control are proposed. To realize the acceleration control, disturbance feedback is necessary. The disturbance observer whose inputs are a current reference to the power converter and a position signal by simple computation works as if it were a disturbance detector. The control poles of the observer are varied in accordance with the velocity of the motor for precise positioning. The proposed method was applied to the linear synchronous motor, which is used for direct drive linear motor, and was tested. Results are presented. >

Suppression control method for torque vibration of AC motor utilizing repetitive controller with Fourier transformer

We propose a method to obtain the compensation signal to suppress the vibration of the motor frame by the repetitive control installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic signal detected by a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. Moreover, we present a new method of the feedforward compensation control adapting to change of operating point of the motor. Effectiveness of the proposed method is confirmed by the experimental results.

Analysis and classical control design of servo system using high order disturbance observer

In earlier papers, it has been reported that a fast and precise servo system, which has low-sensitivity to parameter variation and disturbance, can be realized with simple structure by using a high order disturbance observer. However, a clear and simple design method satisfying specifications for robust stability, influence of measurement noise, and relative stability has hardly been proposed. In this paper, we clarify the class of the robust servo system realized by adjusting the order of the disturbance observer and show design of an estimated disturbance feedback by the disturbance observer, which can represent a classical control approach. We apply this strategy to a design of a position servo system and realize the high performance robust servo system using the high order disturbance observer.

Characteristics of servo system using high order disturbance observer

It is desirable to realize a nominal system which can control acceleration in order to realize a fast and precise servo system, even if the servo system has parameter variation and suffers from disturbance. We have shown previously that compensating disturbance and parameter variation by using a disturbance observer can realize an ideal linear system which can control acceleration. In this paper, first, we transform a plant with a disturbance compensation loop by disturbance observer into a two-degrees-of-freedom control system with a feedforward controller, which indicates that the disturbance observer system includes a series compensator such as P, PI, etc. depending on the order of the disturbance observer. By clarifying the feature of the series compensator, we describe the bandwidth and the stability (the attenuation) of the system and show some simulation results, considering the influence of the measurement noise.

Robust force control based on compensation for parameter variations of dynamic environment

Force control strategies that are robust against disturbance and parameter variations are proposed. These strategies are expansions of disturbance observer-based control strategy, and require little computation. Observers are proposed that estimate parameter variations of the dynamic environment on which the force is imposed are introduced. Since the observer-based control represents a nominal system, a second derivative of force can be controlled. A force control strategy for controlling the second derivative of force is also proposed. The force response similar to the force command is realized by these strategies in spite of the disturbance and the parameter variations of the control object. The effectiveness of the proposed methods is confirmed by simulation and experimental results. >

Suppression control method for torque vibration of brushless DC motor utilizing repetitive control with Fourier transform

The authors propose a suppression control method for torque vibration of brushless DC motors utilizing feedforward compensation control and a generation method of compensation signals for the feedforward control by the repetitive control system with the Fourier transform utilizing a vibration signal acquired by an acceleration sensor attached to the motor frame, and in order to realize online generation of the feedforward compensation signals to reduce the vibration. An auto-tuning method of the repetitive control parameters is also presented. In this paper, an experimental system to detect and reduce the motor torque vibration is constructed, and the effectiveness of the proposed method is confirmed by experimental results.

Robust force control by estimation of environment

A novel force control strategy which is robust against disturbance and parameter variation is proposed. This method is an expansion of a disturbance observer which estimates the disturbance and parameter variation of motors using simple computation. The observer also estimates the disturbance and parameters variation of the environment on which the force is imposed. Since they are compensated by the observer, a similar force response to the force command is realized. The effectiveness of the proposed method is confirmed by some experimental results.<<ETX>>

A new PWM control method for AC to DC converters with high-frequency transformer isolation

The authors present a pulse-width modulation (PWM) control method for a switch mode rectifier on the basis of the idea of coordinate transformation. The proposed method realizes sinusoidal input current waveforms, a controllable input displacement factor, and an arbitrary output voltage waveform. This method is suitable for real-time control. Simulations and experiments carried out to confirm the feasibility of the proposed method are reported.<<ETX>>

A new method of PWM control for forced commutated cycloconverters using microprocessors

A real-time method for generating PWM (pulsewidth modulation) patterns is proposed. The method realizes sinusoidal input and output currents, controllable input displacement factor regardless of load power factor, and maximum output voltage range. The method is effective for reducing higher and fractional harmonic components in the output voltages and the input currents, since it uses three phases of the input voltage sources, which can be connected to the output at the same time. The higher harmonic oscillation in the input filters is reduced by changing the switching sequence of the PWM patterns adequately, and the distortion of the input current is improved. An output current feedback control based on the proposed switching pattern realizes an exact and quick response of the output current. The feasibility of the method is confirmed by simulation and experiments.<<ETX>>

Vibration suppression control method for PMSM utilizing repetitive control with auto-tuning function and Fourier transform

We propose a suppression control method of the motor frame vibration and the rotational speed vibration (ripple) of PMSM utilizing the feedforward compensation control, and a generation method of compensation signals for the feedforward control by the repetitive control and the Fourier transform using a vibration signal acquired by the acceleration sensor attached to the motor frame or the rotary encoder used for the field oriented control, considering periodicity of vibration. The sensor is used on-line or only for the acquisition of the feedforward compensation signal. In order to realize on-line generation of the feedforward compensation signals to reduce the vibration, an auto-tuning method of the repetitive control parameters is employed. Experiments are carried out to confirm the usefulness of the proposed methods and to compare the effectiveness of the two types of vibration sensing methods.